What are the reasons for limiting the charging and discharging rate function of lithium-ion batteries?

The charge-discharge rate function of lithium-ion batteries is directly related to the migration ability of lithium ions at the positive and negative electrodes, electrolyte, and the interface between them. All factors that affect the migration speed of lithium ions (these influencing factors can also be equivalent to the battery The internal resistance), the city affects the charging and discharging rate function of the lithium-ion battery. In addition, the heat dissipation rate inside the battery is also an important factor affecting the rate function. If the heat dissipation rate is slow, the heat accumulated during high rate charging and discharging cannot be reported, which will seriously affect the safety and life of the lithium-ion battery. Therefore, to study and improve the charge-discharge rate function of lithium-ion batteries, it is important to start from two aspects: improving the lithium ion migration speed and the heat dissipation rate inside the battery. 1. The internal resistance of lithium-ion batteries generally adds a conductive agent inside the active material of the positive electrode to reduce the resistance between the active materials, the active material and the positive electrode matrix/current collector, and improve the conductivity of the positive electrode material (ionic and electronic conductivity) ), the promotion rate function. Different materials and different shapes of conductive agents affect the internal resistance of lithium-ion batteries, which in turn affect their rate performance. The current collectors (tabs) of the positive and negative electrodes are the carrier for the lithium-ion battery to communicate with the outside world. The resistance value of the current collector also has a great influence on the rate function of the battery. Therefore, by changing the material, size, extraction method, connection process, etc. of the current collector, the rate function and cycle life of the lithium-ion battery can be improved. In addition, the liquid absorption and porosity of the severing membrane also have a greater impact on the passability of lithium ions, and will inevitably affect the rate function of the lithium ion battery (relatively small). The level of infiltration between the electrolyte of the lithium ion battery and the positive and negative materials will affect the resistance at the interface between the electrolyte and the electrode, thereby affecting the rate function of the battery. The total amount of electrolyte, viscosity, impurity content, pores of the positive and negative materials, etc., changing the resistance between the electrolyte and the electrode in the city is an important research bias to improve the rate function. 2. The ionic conductivity of the electrolyte The ionic conductivity of the electrolyte communicates with the resistance of water, which has a great influence on the speed of lithium ion swimming. The ionic conductivity of the organic electrolyte recovered by the lithium-ion battery at present, whether it is a liquid electrolyte or a solid electrolyte, is not very high. The resistance of the electrolyte has become an important component of the overall battery resistance, and its impact on the high-rate performance of lithium-ion batteries cannot be ignored. In addition to improving the ionic conductivity of the electrolyte, attention should also be paid to the chemical and thermal invariance of the electrolyte. When charging and discharging at a high rate, the electrochemical window of the battery changes in a wide range. If the chemical invariance of the electrolyte is not good, it is easy to oxidize and analyze the appearance of the positive electrode material, which affects the ionic conductivity of the electrolyte. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous post: Introduce the layout of cylindrical lithium-ion batteries and square lithium-ion batteries